1. Field of the Invention
The invention relates to an optical device comprising at least one wavelength converter, as well as a light module incorporating such a device and a lighting device such as a headlamp or a signaling lamp for an automotive vehicle comprising such a module.
2. Description of the Related Art
In the field of automotive lighting, it is known practice, when using laser diodes as a light source, to use an optical element for converting wavelength, also called a phosphor, in order to obtain white light from the monochromatic, often blue, light provided by the laser source.
The laser beam, after potential optical treatments such as scanning and/or diffusion, therefore illuminates the converter. The light beam arising from the converter is then, in the context of such an application, transmitted to an optical projection system with the aim of forming an illuminating beam projected onto the road.
For luminous efficiency and heat reasons in particular, it is often preferable to use a converter functioning by reflection.
Nonetheless, in this case, losses occur, in particular linked to parasitic reflections at the point of incidence of the laser beam on the input surface of the wavelength converter, as well as total internal reflections—that are also parasitic—of the beam inside the material forming the converter, leading to a portion of the beam being absorbed or even being deflected outside the desired angle for output to the optical projection system. These mechanisms are amplified by the fact that the distance between the converter and the projection system must be sufficient to allow the laser beam to hit the converter.